Research On Tunnel Lighting Intelligent Control System Based On LoRa Wireless Technology

With the rapid development of the national economy,China has become the country with the fastest road development in the world and the largest number of tunnels.In the tunnel electromechanical system,the lighting load accounts for the largest proportion,and there is a lot of energy-saving transformation space.However,the current tunnel lighting control system generally adopts wired dimming control or sub-loop control mode,which has the problems of high construction cost,complicated wiring,serious waste of electric energy,inability to achieve smooth control of tunnel brightness,lack of lamp fault detection and active alarm mechanism.Therefore,it is of great significance and practical application value to reserach an intelligent and energy-saving lighting control system.Based on the LoRa wireless technology which has the characteristics of long communication distance,low power consumption and a large number of network nodes and the national highway tunnel lighting design specifications,the core technology of this paper is LoRa wireless networking technology,the design method of the enhanced illumination curve and the incremental dimming algorithm,and a smart lighting control system consisting of a main controller,a LoRa wireless coordinator,a wireless single-light controller and LED lighting fixtures is designed.The system is divided into upper and lower layers:The main controller in the upper layer acts as the core management unit,it runs the dimming control strategy,and sends control and acquisition commands.The LoRa wireless coordinator in the lower layer creates a wireless network,it communicates with each wireless single-light controller in the network,and a wireless single-light controller is connected to the LED lighting fixture to control the luminaire.First,the main controller collects the brightness,traffic flow and vehicle speed information of the hole in real time.According to the tunnel segment defined by tunnel lighting specification and the brightness design requirements of each segment,the main controller calculates the brightness demand value of each segment in the enhanced illumination segment online based to the real-time variation of the three quantities,and a polynomial fitting technique is used to fit a smooth and energy-saving enhanced segment illumination adaptation curve.Meanwhile,based on the principle of minimum overshoot,shortest tracking step and minimum steady-state error,a two-stage incremental dimming control algorithm is proposed.The algorithm adaptively selects the step size coefficient according to the target brightness variation range to adjust the dimming ratio of the lighting fixture,thereby implementing tunnel lighting control.In the MATLAB/Simulink platform,the simulation model of the least squares quadratic polynomial fitting method of the light distribution curve and the incremental dimming algorithm are constructed.Through a large number of simulations,the step coefficient K in the incremental dimming algorithm is obtained,and the validity and feasibility of the algorithm is verified.Secondly,based on the technical requirements of tunnel intelligent lighting control,the serial communication protocol between the main controller and the coordinator and the LoRa wireless control network communication protocol are developed and implemented.The LoRa wireless coordinator and the wireless single-light controller based on STM8 MCU are designed.The hardware circuit and control program design of the coordinator and the single-light controller are introduced in detail.Finally,the system designed in this paper has been successfully applied to 14 tunnels of Yilou Expressway and Wujing Expressway in Hunan Province.Comparing and analyzing the actual operational data of the five tunnels in Yilou Expressway and the Yima high-speed tunnel without control algorithm in 2018,it can be seen that the system has good energy-saving benefits and the energy saving rate reaches 35%.